scholarly journals MICROMECHANISMS OF FERRITE-PEARLITE STEELS FRACTURE UNDER CYCLIC AND IMPACT LOADING

2017 ◽  
Vol 23 (4) ◽  
pp. 345 ◽  
Author(s):  
Pavlo Maruschak ◽  
Andriy Sorochak ◽  
Janette Brezinov ◽  
Anna Guzanova ◽  
Oleh Yasnii
Keyword(s):  
Crack Nucleation ◽  
Fracture Mechanisms ◽  
Qualitative And Quantitative Analysis ◽  
Scale Level ◽  
Fatigue Crack Nucleation ◽  
Micro Scale ◽  
Qualitative And Quantitative ◽  
Railway Axle ◽  
Corrosive Environments ◽  
Crack Nucleation And Growth

<p class="AMSmaintext1"><span lang="EN-GB">During operation, the railway axle is exposed to static, cyclic and dynamic loading that is accompanied by influence of corrosive environments. This causes the accumulation of structural and mechanical damages in the material, formation of corrosion and mechanical micro-defects that are potential sites of fatigue crack nucleation and growth. This requires the development of failure analysis methods that allow determining main mechanisms of ferrite-pearlite steels fracture on the micro scale level. The railway axle’s material – the OSL steel – main regularities of temperature influence on fracture mechanisms in ferrite-pearlite steel type are shown. Qualitative and quantitative analysis of fracture surface of Charpy specimens tested at 20°C and -40°C was performed on micro scale level using SEM investigation. </span></p>

Correlative Fractography: Combining Scanning Electron Microscopy and Light Microscopes for Qualitative and Quantitative Analysis of Fracture Surfaces

2013 ◽  
Vol 19 (2) ◽  
pp. 496-500 ◽  
Author(s):  
Luis Rogerio de Oliveira Hein ◽  
José Alberto de Oliveira ◽  
Kamila Amato de Campos
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Quantitative Analysis ◽  
New Method ◽  
Fracture Mechanisms ◽  
Stereo Pair ◽  
Qualitative And Quantitative Analysis ◽  
Qualitative And Quantitative ◽  
Fracture Surfaces ◽  
Scanning Electron

AbstractCorrelative fractography is a new expression proposed here to describe a new method for the association between scanning electron microscopy (SEM) and light microscopy (LM) for the qualitative and quantitative analysis of fracture surfaces. This article presents a new method involving the fusion of one elevation map obtained by extended depth from focus reconstruction from LM with exactly the same area by SEM and associated techniques, as X-ray mapping. The true topographic information is perfectly associated to local fracture mechanisms with this new technique, presented here as an alternative to stereo-pair reconstruction for the investigation of fractured components. The great advantage of this technique resides in the possibility of combining any imaging methods associated with LM and SEM for the same observed field from fracture surface.

Crack FEA of the First Stage Blade of Gas Turbines

2010 ◽  
Vol 450 ◽  
pp. 429-432
Author(s):  
Ping Zhao ◽  
Wei Li ◽  
Qing Hua He
Keyword(s):  
Gas Turbines ◽  
Life Prediction ◽  
Crack Nucleation ◽  
Creep Damage ◽  
Nucleation And Growth ◽  
Prediction System ◽  
Edge Region ◽  
Element Analysis ◽  
Fatigue Crack Nucleation ◽  
Crack Nucleation And Growth

To investigate the physical cause of premature blade cracking during the acceleration mission test (AMT) in a test cell environment, an in-depth finite element analysis (FEA) of the blade was conducted using a life prediction system. The results obtained showed that the blades had suffered excessive airfoil creep damage, leading to excessive blade lengthening and airfoil untwisting particularly in the trailing edge region. It is predicted that the uneven rubbing action might have contributed to the fatigue crack nucleation and growth process just below the platform in the shank region of the blade under AMT fatigue cycling conditions, and the excessive creep deformation made a significant effect on the overall crack nucleation process.

An Approach for Fatigue Life Prediction

2005 ◽  
Author(s):  
Yanyao Jiang ◽  
Fei Ding ◽  
Miaolin Feng
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Stress Analysis ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Crack Nucleation ◽  
Nucleation And Growth ◽  
Basic Rule ◽  
Fatigue Crack Nucleation ◽  
Crack Nucleation And Growth

Fatigue damage is generally described as the nucleation and growth of cracks to final failure. These two stages of fatigue damage are often modeled with completely different methods with no quantitative relationships between them. In addition, a number of fitting parameters are needed in order to consider different effects. The current work is aimed to develop a robust approach for the prediction of fatigue life from crack initiation to final fracture. The approach bridges the gap between the crack nucleation and growth regions. Based upon the conception that fatigue damage is directly related to the stresses and strains inside the material, it is assumed that both crack nucleation and crack growth are governed by the same fatigue damage mechanisms and a single fatigue damage criterion can model both stages. A basic rule is that any material point fails to form a fresh crack if the total accumulated fatigue damage reaches a limit. Crack growth is treated as a process of continuous crack nucleation without using the stress intensity factor or J-integral concept. The approach consists of two steps: stress analysis and fatigue damage prediction. Elastic-plastic stress analysis is conducted for the component to obtain the detailed stress-strain responses. By using a general fatigue criterion, fatigue crack nucleation and growth are predicted. Notched specimens made of 1070 steel were experimentally tested from crack initiation till fracture. The approach was applied to predict the fatigue life of 1070 steel and the predicted fatigue lives were in excellent agreement with the experimental observations.

scholarly journals Different methods to detect fatigue crack nucleation and growth rate

2019 ◽  
Vol 16 (2) ◽  
pp. 103-109
Author(s):  
Sergio Baragetti
Keyword(s):  
Crack Growth ◽  
Crack Nucleation ◽  
Numerical Models ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fatigue Crack Nucleation ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Rate Evaluation ◽  
Crack Nucleation And Growth

This paper reports a short summary of some procedures that allow to evaluate crack growth propagation rate. Numerical models developed using the equations of linear elastic fracture mechanics are described. Confirmation of the numerical results needs comparison with experimental results. The crack replica method and crack growth gages application are reported and prove to be powerful tools for crack propagation rate evaluation.

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